Focusing-camera.



Patented Sept. 18, 1917.

I 4 SHEETS-SHEET 1.

F 1 j v )3 J. BECKER.

FOCUSING CAMERA.

APPLICATION man JULY 6.1917.

Patented Sept. 18, 1917.

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Positive Negative No.1 No.2 5 2 No.3 No.4

Inventor J. BECKER.

FOCUSING CAMERA.

APPLICATION FILEDVIULY 6. i917.

1 ,240,788. Patented Sept. 18, 1917.

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Pay 9 Fclg'. 10

mentor UNITED STATES PATENT OFFICE.

JOSEPH BECKER, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO EASTMAN KODAK COMPANY, OF ROCHESTER, NEW YORK, A. CORPORATION OF NEW YORK.

FOGUSING-CAMERA.

Specification of Letters Patent.

Patented Sept. 18, 1917.

Continuation in part of applications Serial No. 26,647, filed August 11, 1900, and Serial No. 88,805, filed April 4, 1916. This application filed July 6, 1917. Serial No. 178,990.

To all whom it may concern:

Be it known that I, Josnrn BECKER, a citizen of the United States, residing at Washington, in the District of Columbia, have invented certal'n new and useful Improvements in Focusing-Cameras, of which the following is a specification.

The present application, identified for convenience of reference as Case AX, con'stitutes the third and concluding part of a single continuous application whose fundamental subject-matter, seen in Figure 57 of my Case A, now Patent 1,178,474, bears the three successive filing dates, to Wit: August 11, 1900, of my said case A; April 4, 1916 of my herein merged Case Ak, Serial No. 88,805; and July 6, 1917 of my present Case AX.

A complete list of all my applications or patents referred to more or less specifically in the present specification, comprises: my Case A, Serial No. 26,647, filed August 11,-. 1900, now Patent 1,178,474, issued April '4, 1916; my Case C, Serial No. 63,106, filed June 4, 1901, now Patent 1,178,476; my Case Ag or division one of A, Serial No. 86,366, filed March 24, 1916; my Case Ah or sole division of C, Serial No. 87,977, filed March 31, 1916; my Case Ak or division three of A, Serial No. 88,805, filed April 4, 1916; my present Case AX, Serial No.

178,990, filed July 6, 1917.

Fig. 57 of my said Case A is diagrammatic, as noted in line 91, page 18,- of my said Case A, and it therefore is not well suited to present purposes, for several reasons, to Wit: First, it is entirely dependent on other widely separated parts of the Case A specification, for a disclosure of the theoretical principles involved; secondly, it incorrectly shows the contacting faces of the terminal teeth on its lever arms 131, 132' as flat, instead of rounded to agree with the showing in Fig. 55, where they might even be made more curved, for clearness; thirdly, its cam edge 134 is not sufliciently inclined or non-radial, for any ordinarily assumable lens and camera dimensions.

The main object of the present application, Case AX, is to cure all of the just enumerated deficiencies; and a secondary object is to add an angular adjustment for the mirror 138 of the said Fig. 57, to permit of' inclining the line of sight as in my said Cases C and Ah.

The present invention consists in focusers of the special two image type referred to in Note 8, page 21, of my said Case A, as comprising two base line mirrors mounted obliquely at the end of the focuser base line so that each faces the object and acts independently of the other to form its own separate image of the object, as in Figs. 89, 4.0, 41, 44, 4.5 46, 52, 54, 57, 59, c0 of my said Case A, where Figs. 42, 47 and 48 are likewise relevant.

Fig. 57, of this series, with slight improvements, is selected as main figure, or Fig. 1, of the present application, Case Ax, because it comprises, united and combined in one structure, the greatest number of important features, to wit: (1) each of the two base-line mirrors M, M mounted so as to face the object, as just stated; (2) the optically closer of the two base line mirrors M made sufficiently large in extent to show the peripheral parts of the camera field and virtually provided with a relatively small central passage to admit rays coming from the more distant base line mirror M (3) a special combination of totally reflecting prisms acting as such virtually perforated and optically closer base-line mirror; (4) a divergent lens to form a reduced and relatively close image of the, full size and distant, compound image formed by the said base-line mirrors; (5) means, such as a third angularly adjustable plane mirror R, for erecting such finder image, and for adjusting the inclination of the line of sight Ejj to produce a drop finder eflectsuch as noted in my said Case'Ah; (6) pivoting, and symmetrical arrangement of, the two baseline mirrors M, M to avoid parallactic error; (7) the extremely simple non-radial cam 70, 70, as connecting gear between the focuser parts on the one hand, and the camera parts on the other hand.

Feature 6 is fully claimed in my said parent Case A; and feature 7 is fully claimed in my said Case Ag or division one of A; hence, no claim will be made to either of these features 6 or 7 in the present application, Case Ax.

In the accompanying drawings:

Fig. 1 (reproduced from Fig. 57 of my said Case A, excepting as to four main features, to wit: (1) the angular adjustment of mirror R; (2)the. exact plotting of the conjugate distances CF and FO; (3) the necessarily greater inclination of the cam face lclc called for by such exactly plotted distances; (4) the complete diagram of all images formed by the focuser mirrors and 5 lens, is a side view of a focusing camera provided with my present improved form of focus and field finder showing the camera sharply focused on O, at while the mirrors M and M are held, by the correctly in- 10 clined cam edge kit at the proper inclination to secure apparent coincidence of the two reduced, but erect and positive, finder images j and j of the said object point 0.

Fig. 2 is a front view of the same camera showin how the fundamental base line AA of the ocuser is met and bisected at B, by the principal axis of the camera, and is wholly contained in the vertical meridional plane of the camera objective. 2 Fig. 3 shows the finder image as it appears to the eye at E, Fig. 1, assuming that the object to be focused on is the letter L which it will be noted is seen both erect and positive, exactly as if viewed without a finder, excepting that it is smaller and that it has at j, a break which indicates that the camera is out of focus. Fig. 4% is a scale of parts used in measuring the fundamental dimensions of Fig. 1, 3 each part being about 3 millimeters long in the camera if the latter be of the size that takes the standard 5 by 7 inch plate.

Figs. 5 and 6 are tables of the fundamental dimensions, both linear and angular, that occur in Fig. 1.

Fig. 7 (corresponding to the two Figs. 41 and 13 of my said Case A) shows the simplest form of the two base-line mirrors M and M it also answers as a diagram of what occurs when the mirrors M, M of Fig. 1 are set in parallel relation, orfor-infinity, showing how the alined object points 0, P, Q, are, in such case, reflected as two parallel series of images I, J, K and I, J, K.

F ig. 8, comprising four separately numbered compartments 1, 2, 3, 1, illustrates "what I mean by the terms positive or negative and erect or inverted as applied to four different finder images of the same letter F used as field object, F being, for present purposes, even more convenient than J used in Fig. 3.

Fig. 9 shows a perforated prism equivalent of Fig. 7.

Fig. 10 shows the unperforated built-up prism equivalent. of either Fig. 7 or Fig. 9 that is used in Fig. 1.

Fig. 11 is a perspective of the upper builtup prism of Fig. 10.

60 Fig. 12, shown as if made of a single piece of glass, illustrates how the central cemented surface element of the larger prism. in

Fig. 11, has totally lost reflecting power. The camera proper. Fig. 1, comprises an 5 L-shaped frame 10, 11, whose upright part 10 supports the lens 12, and whose horizontal part 11 is provided with suitable guideways for the movable frame 13 which carries the ground glass, plate or film l4, and is connected with the upright 10 by the usual bellows 15.

The upright part 10 has rigidly fastened thereto a vertical shelf-like bracket 20 which serves as base plate and support for all parts of the combined focus and field finder, whose optical elements comprise three principal parts, to wit: first, two pivoted or base-line mirrors M, M, Whose stationary central points are indicated by dots A, A, and which form two full size but inverted and negative images I and I of the object point 0 to be focused on, as in compartment No. 4: of Fig. 8; secondly, a stationary divergent lens D which forms the relatively close but reduced copies 2', z" of images I, I, such reduced images i, a" being likewise inverted and negative, as in compartment No. 4 of Fig. 8; thirdly, a stationary plane reflector R which reflects images i, i, to form the images j, j, constituting the true finder image, Fig. 3, where the object to be focused on is the letter L, seen both erect and positive as in compartment No. 1 of Fig. 8; that is to say the upper part of the letter is up, and its righthand side is at the right, so that there is no inversion of any kind present, in the final finder image jj.

The exact relation of the two full size and alined images I, I in Fig. 1, is made plain by adding the two nonregistering or offset images J, J of the closer axial point I. The intersections of the lens axis FF by the two mirrors M and M being at n and a, respectively, it is furthermore evident that the image of OPn in mirror M is IJn, while the image of line OPn in mirror M is line IJn.

The upper base line mirror M is rigidly mounted on a bell-crank 21, 22, which is piv- 11o oted to the base or shelf 20 by a pivot 23, whose axis produced passes through the central point A of mirror M and determines the axis of rotation of such first base-line mirror M. The lower base-line mirror M is simi larly mounted on a bell-crank 21, 22, which is pivoted to the base or shelf 20 by pivot 23 whose axis, produced, passes through the central point A of the mirror M and determines the axis of rotation of such second baseline mirror M.

Arm 21 has a gear-tooth extension 24 which is held pressed against a similar geartooth extension 24' of arm 21, by means of a tension spring 25 connecting the horizontal members 22, 22 of the two bell cranks.

The lower arm 22 has a rearwardly projecting extension 26, 27, which plays freely in a channel 28 formed in bed 11 of the camera and whose upper rear edge 71:70 constitutes a non-radial cam edge adapted to bear against the lower right-hand edge or corner is of the movable frame 13, contact being insured at In by the same before-mentioned tension spring 25, which, therefore, sufiices to take up all lost motion and keep all parts of the combination in close working contact. \Vhen the camera is to be focused on left-hand infinity for instance, 0 comes up into coincidence with F, corner 70 moves up to 70', and the point 70 of the cam rises up into coincidence with 70', where it makes contact with corner 7;" frame 13 and holds the mirrors M and M in parallel relation. The angle tau (1.) o'r lcAk is evidently equal to one-half ,of

. angle omega (to) or FOA, and the principal focus F is, in this case, identical with point G of Fig. 23 in my said case A, in which figure the pivot A corresponds to pivot A, Fig. 1, of the present case. It also evidently corresponds to pivot A of the present case.

The pivoted mirrors M and M therefore act as if each independently cooperated with an imaginary stationary mirror set obliquely at B on the camera axis and corresponding to mirror N in Fig. 4.- of my said Case A. That is to say the basic triangle of the focuser is not OAA but triangle OGA, or the equal triangle OGA and the basic angle of the corresponding theoretically exact or radial cam focuser is the obtuse angle r at G, which is identical with the angle 7' at G in the basic diagram, Fig. 23, of my said Case A.

When the two base-line mirrors are turned from their parallel relation, such as the relation shown for mirrors M", M in Fig. 7, into an inclined relation, such as the relation shown for mirrors M, M in Fig. 1, it should be noted: first, that the two images I and I of Fig. 7 are moved inwardly, at equal rates, until they both fall into alinement with A and A as shown in similarly bisecting angle OAI, fixes the angular position ,-'of mirror M.

Bisection at A is rendered evident by notingthat the angles a and b are separatelyequal to 0,-hence equal to each other; and bisection at A could be proved in the same manner.

*The mirror R is shown as fixed at 4.5 de- 'greesto determine a sight line Ejj that is horizontal. Its base 30, however, is pivoted of the advanced at 31 and has a clamp screw 32 passing through the arcuate slot 38, to permit of fixing the mirror at any other desired inclination with the object of lowering the finder image jj, and producing a drop effect similar to that noted in my said Case C, and in my said case Ah division of C.

With reference to the nature of the finder image obtained, it should be noted: first, that any arrangement such as shown in Figs.

52, 54 and 59 of my said Case A has the disadvantage of forming a finder image that is both inverted and negative as in compartment No. 4 of my present Fig. 8; secondly that the arrangement shown in Fig. 60 of my said Case A forms a finder image that is erect but negative as in compartment No. 2 of my present Fig. 8; thirdly that the arrangement of present Fig. 1 forms a finder image that is both erect and positive as in compartment No. 1 of my present Fig. 8. The present Fig. 1, therefore, has special practical advantages over all others and constitutes, in this particular respect, a novel form of field finder that is generally useful in all cameras, even in those of the fixed focus type.

The two base-line mirrors in their simplest form comprise a simple reflecting plane M Fig. 7, perforated at m, and a simple unperforated reflecting plane M and the evolution from such simplest form, to the built-up form of Fig. 1 is most easily traced through Figs. 9 to- 12.

Substituting totally reflecting prisms for the reflecting plates M M of Fig. 7, produces the form seen in Fig. 9, where the upper prism must be provided with a perforation or well, but the result is not satisfactory because of the ditliculty of making a sharp flat wall perforation and because the walls, unless they taper exactly to the observers eye, must conceal the meeting edges of the two images to be brought into registration.

. Another and more serious objection is that the perforation acts as an opaque body in the prism and therefore cuts off a good part of the image. To avoid all these difficulties, I have devised the highly improved form, Fig. 10, in which a small prism 11 1 is cemented with Canada balsam to the under side of an unperforated main prism 115. The compound prism thus formed, with prism 103 forms a combination exactly equivalent to what the form shown in Fig. 7 would be, if the upper reflecting plate M in such Fig. 7, could be made infinitely thin.

The compound or built-up prism of Fig. 10 is shownseparately, and in perspective, by Fig. 11.

The addition of the small prism is equivalent in effect to the perforation of the large prism. It virtually provides the large prism with a wall-less perforation. That a hole should be virtually produced by the addition of matter is so paradoxical that I must eXplain the effect in full.

There the prisms are in contact the cement, being of the same refractive index as glass, unites the two prisms so intimately that the cemented surfaces virtually cease to exist and the glass of the small prism 11 i becomes, in effect, continuous with that of the large prism 115. The two prisms are, as it were, one solid mass of glass of the outline shown in Fig. 12, where the combination 114, 115 is obviously as transparent to a vertical ray of light 117 as any planeparallel plate of glass might be. The horizontal ray 118 likewise passes through without deviation.

Ray 119 in Fig. 10 might appear to be reflected at the cemented surface of the small prism 114, but it really is reflected by the adjacent uncemented surface of the large prism 115.

Nora 1.Although the two-prism form of reflector in Fig. 8 is my own original invention, such invention was fairly anticipated in a publication of Lummer and Brodhun, Ze /Ifschrift fair [mum memen- Zeal/ride, vol. 9, Berlin 1889, pages 23 to 25;

also Figs. 1 and 3 on page 43; and therefore I do not make any claim to the two-prism reflector per se.

NOTE 2.-The preferred form of nonradial cam 7070 is an adjustable form such as shown in Fig. 57 of my said Case A,

.but as before noted all claims on the nonradial cam are made in my said Case Ag.

No'rn 3.-The images seen in Figs. 38 and 42 of my said (JaseA correspond, in nature and direction, respectively to those shown in compartment No. 1, and compartment No. 4 of the present Fig. 8.

NOTE 4.The disclosures made herein, in connection with present Fig. 8, as to the nature and direction of focuser images, though consistent, as remarked in Note 3 above, with those originally made in Figs. 38 and 42 of my said Case A, are in direct conflict with the disclosures'made in Figs. 7 and 8 of U. S. Patent No. 1,166,032, granted December 28, 1915, to oodbury; but the house seen in the said Woodbury Figs. 7 and 8, if correctly drawn should have been shown upside down instead of erect.

What I claim as my invention and desire to secure by Letters Patent is:

1. The combination with a photographic camera comprising relatively movable parts adapted to be relatively moved to set the camera in focus on an object point in the camera field, also an optical focuser of the type comprising means for sighting from two laterally separated points on the focuser or camera convergingly on the same said object point to be focused on, said focuser comprising mirrors located at the said sighting points; one of the said mirrors consisting in a total reflection prism, and meahs for rendering a part of its hypotenuse face transparent.

2. he combination with a photographic camera comprising relatively movable parts adapted to be relatively moved to set the camera in focus on an object point in the camera field, also an optical focuser of the type comprising means for sighting from two laterally separated points on the focuser or camera convergingly on the same said 1 object point to be focused on, said focuser comprising mirrors located at the said sighting points; one of said mirrors consisting in a total reflection prism, and means for rendering a part of its hypotenuse face transparent, said means consisting in a. smaller similar total reflection prism cemented with its hypotenuse face in contact with the hypotenuse face of the said larger prism to annul the reflecting power of that part of the hypotenuse face of the larger prism that is covered by the hypotenuse of the said smaller prism.

3. The combination with a photographic camera comprising relatively movable parts adapted to be relatively moved to set the camera in focus on an object point in the camera field, also an optical focuser of the type comprising means for sighting from two laterally separated points on the focuser or camera convergingly on the same said object point to be focused on; said focuser comprising mirrors located at the said sighting points, and both facing the object; of a divergent lens in the path of rays emitted by the object and reflected by the said mirrors, with its principal axis directed substantially through the said two laterally separated sighting points; and a third mirror fixed in the path of. the object rays emitted by the said lens, to reflect such object rays into the observers eye E as c ming from two erect images j, j; and means for fixing said third mirror at an angle that is variable to secure any preferred inclihation of the line of sight Ejj'.

In testimony whereof, I have signed my name to this specification.

JOSEPH BECKER.

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